1. Technical Field
The present invention relates to a module for mounting a reciprocable tool. More specifically, the invention relates to a mounting module which includes a retraction and extension mechanism permitting selective operation of a reciprocable tool. The mounting module is especially adapted for use in gang punch presses such as those used in the manufacture of trailers or airplanes.
2. Background Art
Reciprocating presses used for punching holes in sheet metal parts, paper, fabric and other objects normally include standardized punches held in punch retainers. The punches are preferably removable for replacement or to permit elimination of a hole punching operation. In gang punch presses used in the manufacture of large parts having a large number of holes, changing hole punch patterns as required for different parts is time consuming. If the changes are not done carefully, misformed parts can result which have too many or not enough holes.
Prior designs for providing retractable punches tend to be bulky and difficult to changeover to different hole punch patterns. Another problem suffered by retractable punches is that they are not sufficiently durable for cutting rigid material such as sheet metal.
An example of one type of prior art multiple punch having selectively operable individual punches is disclosed in U.S. Pat. No. 1,313,699 to Kavanagh. The device used in Kavanagh is commonly referred to as a gagging plate or bar. The gagging plate includes openings which permit a punch to retract into a non-operative position. Portions of the bar between the openings, or raised areas, are provided for supporting a punch and holding it in its operative position. Gagging bars do not permit complete flexibility in hole punch patterns and do not permit the use of quick replacement punches. Care must be used in changing over to eliminate errors in the hole pattern.
Another approach to providing a selectively operable punch is disclosed in U.S. Pat. No. 4,555,966 to Klingel which describes a punch press having a plurality of punches which are selectively shifted between operative and inoperative positions by means of a rotatable cam. The rotatable cam includes a separate drive mechanism and notched and unnotched areas providing inoperative and operative punch positions respectively. The punch mounting arrangement disclosed in Klingel suffers from the disadvantage of requiring considerable radial space between adjacent punches which prevents the use of such apparatus in closely spaced hole patterns. The separate drive mechanism for rotating the rotatable cam is complex and bulky adding excessive expense to the cost of the device.
Another general approach to providing selective punching mechanisms is to provide an interposable element between a punch and the punch drive mechanism. One example of this approach is disclosed in U.S. Pat. No. 3,311,297 to Williamson which describes a selective punching mechanism using a spherical interposer. The interposer is shifted between operative and inoperative positions by energizing a electromagnet which overcomes a permanent magnet provided to bias the interposer into its inoperative position. The device disclosed in Williamson would be inappropriate for use with closely spaced punches due to the space required for the interposer shifting mechanism. Also, the interposer is not well suited for use with quick replacement punches and there is no safeguard against setting improper hole punch patterns. In U.S. Pat. No. 3,659,779 to Berkman a selectively operable punch mechanism is disclosed which uses an interposer comprising a slotted element having cam surfaces for operative and inoperative positions. The slotted elements are shifted to their operative position by means of a pneumatic piston and include a permanent magnet biasing means for holding them in their inoperative position. Both Berkman and Williamson include the use of permanent magnets for biasing the punches in their inoperative position which adds to the cost and complexity of the devices.
The above prior art devices have shown certain shortcomings and disadvantages especially when punching closely spaced holes in relatively rigid materials. Replacement of punches and changeover from one hole pattern to another hole pattern is complicated with prior art devices.